Photon energy calculator

Wavelength (λ) Option A

— OR —

Frequency (f) Option B

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Photon Energy (E)

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Joules: ---

How it works?

This calculator computes single photon energy based on the Planck-Einstein relation. Since frequency and wavelength are inversely proportional, the energy is derived using physical constants:

$$ E = h \cdot f $$ Using Frequency

$$ E = \frac{h \cdot c}{\lambda} $$ Using Wavelength

Constants:

h : Planck's Constant ($ \approx 6.626 \times 10^{-34} \, \text{J}\cdot\text{s} $)
c : Speed of Light ($ \approx 3.00 \times 10^8 \, \text{m/s} $)
E : Photon Energy (Joules)

The Electron-Volt (eV) Conversion

Photonics often uses Electron-Volts (eV) instead of Joules. The calculator converts this using the elementary charge:

$$ E_{\text{(eV)}} = \frac{E_{\text{(Joules)}}}{1.602 \times 10^{-19}} $$

Why calculate Photon Energy?

In macroscopic physics, we treat light as a continuous wave. However, in the microscopic world of quantum mechanics, light behaves as individual packets of energy called Photons. The energy of these packets is not random—it is strictly defined by the light's color (wavelength/frequency).

This calculator uses the Planck-Einstein relation (E=hf) to bridge the gap between the wave properties of light (nm or Hz) and the energetic properties (Joules or Electron-Volts).

Key Applications

1. Semiconductor Bandgap Engineering

For an LED or Laser Diode to emit light, an electron must drop across a "Bandgap." The size of this gap (in eV) determines the exact color emitted. Engineers use this calculation to select materials (like GaAs or InP) for specific wavelengths.

2. Solar Cell Efficiency

Photovoltaic cells can only convert photons that have enough energy to knock an electron loose (The Photoelectric Effect). If the photon energy is lower than the material's bandgap (e.g., 1.1 eV for Silicon), the light passes right through, generating no power.

3. Photochemistry

In biological imaging and UV curing, chemical reactions require a specific "Activation Energy." This calculator helps determines if a specific UV wavelength (e.g., 365 nm vs 405 nm) carries enough energy per photon to trigger the reaction or cure the resin.

4. X-Ray & Spectroscopy

As we move to high-energy physics (X-Rays and Gamma Rays), describing light by wavelength becomes cumbersome (0.00001 nm). Scientists switch almost exclusively to Photon Energy (keV or MeV) to describe penetrating power.

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